Thanks again, all of you.
An FP-30x came home today and think I'm going to like it a lot. Connection was very straightforward, and if there's any difference in latency between the USB and DIN mode of connection (I'm set to 64 buffers), I'm not perceptive enough to pick up on it.
I suspect it will take a little while before the action feels fully natural because I had my previous keyboard for 15 years and the way it felt had come to be my 'normal.' With that said, the Roland action (PHA-4) immediately felt comfortable and a good 'fit' when I was trying instruments in the stores, so I'm optimistic on that front.
I was surprised at how much I disliked the Korg RH3 keybed when I played it after the Roland's - perhaps the demo models just needed breaking in, but it felt very clunky - almost like playing a typewriter! And I was quite relieved that I didn't gel with the RH-III keybed in the Kawai ES920 I tried. I had gone in expecting that this would be the one to beat, but I found playing it a little more 'work.' Likewise, I had half-expected to be smitten with the Grandtouch action in the Yamaha P525, but didn't have the 'wow' moment I was worried would cost me mucho NZ dollars!
So, should anyone else stumble on this thread in their quest for a new piano, don't be like me and assume that the 'prestigious' and most expensive actions are the ones that will suit you best :-)